The developing brain is bombarded with a temporal stream of visual information that must be organized into meaningful agents, objects, and events. When tracking a bouncing ball against a cluttered background, the critical challenge is to balance the integration of concomitant information with the segmentation of disparate information; a compromise between stable representations, and sensitivity to change. Because this process is so fundamental to perception and cognition, even small differences can have large consequences for how one sees the world, contributing not only to individual differences and developmental change, but also neurodevelopmental disorders, such as Autism Spectrum Disorder (ASD). Even though sensory processing differences have recently been added to the diagnostic criteria of ASD, surprisingly little is known about the development of temporal organization in visual perception, and its role in the etiology of ASD. The existing work that constitutes the scientific premise of this proposal has a critical limitation: when age groups, or groups with and without a diagnosis of ASD, have been compared, it is challenging to know whether observed differences are due to temporal processing per se, or differences in general factors ? e.g. motivation and/or response execution. Through the adaptation of a novel adult paradigm (that we have successfully used in psychophysical and neuroimaging studies), we will be able to measure both integration (the ability to combine visual information over time) and segmentation (the ability to discriminate sequential visual information) using the same stimuli, task, and within the same child. This allows us to disassociate measurements of temporal processing from other factors that may influence overall task performance. We will use this innovative approach to track the development of visual temporal processing in very young children with ASD, and those without. We will test a large (N=130) sample of 2.5-year-olds (the earliest age at which a reliable diagnosis of ASD can be made) and re-test them one year later. We hypothesize that 1) temporal integration windows narrow over development, advantageously increasing temporal resolution; and 2) that temporal integration windows are disadvantageously broad in ASD and this contributes to several common symptoms in ASD. Building on this foundational work that is an ideal fit with the exploratory high-risk, high-reward projects supported by the R21 grant initiative, in future work, we plan to specify the underlying neural mechanisms using EEG, and study the adaptability of temporal integration windows to changing task demands.